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Test Indications:

For the in vitro detection of IgM antibodies specific for rubella. IgM antibodies are associated with acute viral infections. IgM detection is useful in the following situations: evidence of infection can be obtained from only one acute phase specimen if the IgM results are positive; the IgM test can also be used to differentiate between primary infection and re-exposure. Rubella-specific IgM is found in virtually all infected patients by three weeks post-development of a rash. Rubella-specific IgM is also found in 80% of post-vaccination patients by three weeks. Congenitally infected infants will show an IgM response at 2 to 12 weeks postnatally.

Lab Testing Sections:

Serology - Sendouts

Referred to:

LabCorp (Test#: 096537)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

1 – 2 days

Special Instructions:

Specify acute or convalescent specimen. Collect acute phase specimens as soon as possible after onset of illness and no later than 5 to 7 days. Collect convalescent-phase specimen 14 to 28 days or longer after onset. Rubella acute specimen should be drawn while rash is present.

Interpretive

The absence of IgM at birth does not rule out congenital rubella since the frequency of IgM detection in cord blood decreases as the time between conception and fetal injections increases. Acquired rubella infection in infants is rare but must be considered if the blood is positive for IgM but was not obtained during the immediate postnatal period. Rubella-specific IgM may persist for months after an acute infection and, possibly, after vaccination as well. False-positive rubella IgM responses have also been reported in pregnant women. These reactions are usually accompanied by false-positive reacitions to other viruses (eg, CMV and measles).

Methodology:

Chemiluminescence

References:

LabCorp (January 2013)

Updates:

3/4/2004: Test moved from Lab Corp (Viromed) to Mayo Medical Laboratories.
7/1/2008: Test moved from Mayo to MDH. Mayo no longer performs the test due to interferences on positives and widespread immunization in the population making it obsolete.
1/1/2013: Test moved from MDH to LabCorp. Note change in reference range and methodology.

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